Wing Cmdr Mike Bracken said Nato's command centre in Naples, Italy, had lost contact with the unmanned aircraft at 07.20 GMT.

His statement came as Libyan state TV showed images of what it claimed was the wreckage of a Nato Apache attack helicopter that had been shot down.

Wing Cmdr Bracken said no attack helicopters had been lost.

"This drone helicopter was performing intelligence, surveillance and reconnaissance over Libya to monitor Colonel Gaddafi's forces threatening the civilian population," he said.

"We are looking into the reasons for the loss. We can confirm we have not lost any attack helicopters."

Earlier, Libyan state TV aired footage of what it said was an Apache helicopter shot down by pro-government forces in the western district of Zlitan.

Nato deployed Apache attack helicopters in Libya earlier this month during its UN-sponsored mission to protect civilians from forces loyal to Col Gaddafi.

The drone is the first aircraft reported lost by Nato over Libya since it took over the no-fly mission on March 31.